The products of the metasomatism of igneous rocks are found for the most part only in small quantities since diffusion through a solid rock of the solutions responsible for metasomatic changes is a slow process. In the Whin Sill there are two types of metasomatic alteration product which though insignificant in total amount are nevertheless widely distributed. The first type, which was formed along the walls of an early joint system by the action of juvenile solutions, is part of the history of the cooling down of the Whin Sill and will be described in a subsequent paper. The second type was produced by the action of lead vein solutions. Although unconnected with any stage in the cooling down of the Whin Sill, this type has an important bearing on the general mechanism of replacement and especially on the part played by diffusion, whose effects may be seen in both types as an extended transition between altered and unaltered dolerite.

The very interesting igneous rocks of the Mozambique Company's territory have not had much attention paid to them in the past, though some of them were noticed in the first paper dealing with the Karroo beds near Tete, that by Lapierre. That writer was in advance of some subsequent observers in his recognition of the peculiar character of the Lupata lavas: so far, indeed, have some others been from this that the various geologists working in the Tete district have actually been accustomed to call the Karroo basalts the “Lupata Volcanics”, as is done in the most recent paper referring to that area. The age of the basalts was demonstrated by the writer in some notes contributed to this Magazine in 1922, and to establish this it was necessary to discuss the position of the Lupata lavas. Messrs. Teale and Campbell Smith subsequently published the first reliable petrographical descriptions of some specimens previously collected by the former, and the present paper is intended to supplement by further field and petrographical notes the valuable work of Dr. Teale, who has long since sought pastures new. It may be mentioned that one of the chief features of the area is the way in which the various igneous rocks are sometimes intermixed. This is a leading factor in contributing to the uncertainty which surrounds the dating of some of the intrusives. Thus a large number of intrusions of various kinds traverse the Karroo basalts and these are undoubtedly of two and perhaps of three different periods. Faulting and overlaps also cause further complications, as may be seen in the small sedimentary area near Mutarara, where Tertiary, Cretaceous, and Karroo volcanics occur closely associated.

The present notes have accumulated since 1923 during a survey of the solid geology of the region between the western slopes of the Vale of Conway and Moel Wnion, including the district around Tal y Fan mountain, Foel Lwyd and Drosgl, and extending northward to the coast. The glacial deposits and alluvium have been mapped on the 6 in. scale, and a sketch-map is here given (Fig. 1). The areal distribution of the drift is described and an attempt is made to account for some of the glacial and physical features. Some notes are added upon the general character and origin of the Conway Valley.

Work by the author on the rocks of the Upper Ordovician and Lower Silurian in Central Wales has led to a comparison with deposits of similar horizons in other areas. Several points of interest have arisen out of the investigation and may be of value in delimiting the zones of the Upper Ordovician and also in indicating the best workable definition of the base for the Silurian.

One of the most imposing and best known exposures of glacial deposits in the north of England is the line of high cliffs along the Yorkshire coast, between Patrington and Withernsea, the highest point of the cliffs being at Dimlington Beacon. Here 140 feet of glacial material is exposed in the cliff face and the foreshore is entirely of boulder clay, the base of the deposits being a long way below sea-level. The work of this paper relates to the clays and sands in this cliff exposure. The deposits are easily distinguished as being of three varieties; at the base and along the foreshore, a dark leaden grey to black, tough boulder clay, including lenticles of sand frequently containing shell fragments; this is succeeded by a thick clay of rich purple or red colour, with noticeably more contained boulders, and near the top, much included sand in lenticles, passing into a bed of pure sand; the highest part of the cliff is of earthy clay, foxy red in colour, and with relatively few boulders. These are respectively the Basement clay, the Purple clay, and the Hessle clay. Between the Basement clay and the Purple, and at the top of the Purple clay, there are beds of sand a few feet thick; these are not to be seen at all parts of the coast, but are generally present in the highest sections. Fig. 1 is a vertical section of the Dimlington cliff, and the Roman numerals indicate the specimens petrologically examined.

Very little work seems to have been done on the petrology of the rarer constituents of the older Palaeozoic sediments and their associated igneous rocks, partly no doubt on account of the extra amount of work entailed in crushing these extremely hard compact rocks, and partly owing to the comparative paucity of the “heavy” residues obtained, which give small reward for the energy expended. Such work, however, is highly important as indicating further sources of supply, to which workers on the petrology of the newer rocks may look, and it may be here emphasized that Wales has unfortunately suffered neglect in this respect. It is to help remedy this defect that the present paper is put forward.

Mr. G. M. STOCKLEY, F.G.S. in 1925 made the interesting discovery of fossils near the top of Blue Mountain Peak, the highest summit in Jamaica, at the considerable altitude of about 7,000 feet. Unfortunately the material he collected was lost on the way down by a horse slipping and throwing his fossils down a ravine. He told me, however, that he was almost sure there was a species of Inoceramus among them. Dr. C. A. Matley, F.G.S. collected some specimens at the same locality a year or two later. On looking over his collection, however, I could not find any fossils which might fix beyond doubt the age of the beds. During a recent visit to Blue Mountain Peak I was able to spend enough time at the locality to make a small collection of fossils which I now endeavour to describe.

In a paper dealing principally with the question of the age and relationships of some Lower Cretaceous bivalve-shells found at Malone, in Texas, I discussed briefly the distribution of those sublittoral Neocomian deposits that are well characterized by the presence of certain Trigoniae of southern facies. It was shown that traces of this Neocomian fauna, revealing a general community chiefly by the widespread occurrence of these peculiar groups of Trigonia, unknown in the European area, had been found in different latitudes, both in the eastern and western hemispheres, indicating that there had been northward dispersal along the area of the present American continent from Patagonia to Texas, and in the eastern hemisphere from South Africa to the north-west Himalayan border. Some evidence of the same faunal facies had also been found in New Caledonia. I pointed out that the faunas of these southern Lower Cretaceous Trigonia beds of different regions had been misinterpreted again and again, and that their representatives found in Texas, in South Africa, and in Cutch had been thought by some investigators to be of Jurassic age.

It is some thirty years ago and about ten years after the mapping of this area by the officers of the Geological Survey that one of the present writers ascended Quinaig at Inchnadamph and saw for the first time the so-called “Pipe-rock” which caps the summit of that mountain. Here one can walk over the exposed surfaces of the quartzite and it is impossible not to observe the curiously spotted or pitted surfaces of the white slabs which, in many places, look like nothing so much as the soles of a labourer's shoe covered with projecting hobnails (see Plate IV, Fig. 1).

Some time ago I was asked, in connection with a question regarding the Dwyka conglomerate, to say if any of the volcanic deposits of Java in any way resemble a glacial deposit. As I was in Java from 12th May to 6th June as a Member of the Fourth Pacific Science Congress, and travelled from Batavia to Soerabaya via Buitenzorg, Bandoeng, Garoet, Koeningan, Loh Ulu, Jocja, Kediri, and the Tengger Mountains, as well as going to Krakatau, I had a good opportunity of replying to the question, but it must be understood that this note is not intended as a contribution to literature on the Dwyka conglomerate, which I have never seen, but purely as an answer to the query “are there any volcanic deposits in Java resembling glacial deposits ?” The reply briefly is that such deposits do exist, namely the “mudstream-deposits” of Gunong Keloet, near Kediri.

In an article with the above heading (GEOL. MAG., Vol. LXIV, 1927, p. 518) Mr. L. J. Chubb discussed the geology of these two small Pacific islands, which are somewhat centrally situated in the western part of the South Pacific Ocean.

The alkaline volcanic rocks of the Lupata Gorge were described in 1915 by E. O. Teale and R. C. Wilson, and in 1922 F. P. Mennell showed that at the entrance to the gorge these rocks were preceded by a sheet of columnar rhyolite intercalated between two series of sediments, for which he proposed the name of the Upper and Lower Lupata Sandstones respectively; the Lower series rested on Karroo basalts, and these upon Karroo sandstones. In 1923, E. O. Teale and W. Campbell Smith gave a detailed petro-graphical description of certain of the alkaline lavas and of the intrusive olivine-nephelinite (nepheline-basalt) of Sena Hill on the south side of the Zambezi.

The specimen to be described is from part of the McKenny Hughes Collection, preserved in the Sedgwick Museum, and was without any indication of horizon or locality. It is a slab of hard, light-grey, spotted shale, containing numerous examples of Dictyonema flabelliforme (Eichwald). The matrix is quite unlike any Dictyonema Shale known to the writer from extra-British localities, and from the general habit of the graptolites, supported by the lithology of the shale, the specimen is considered to be from some locality in Wales. In the view of Dr. G. L. Elles, who has examined the specimen, it may be part of a collection of D. flabelliforme made by McKenny Hughes from the Portmadoc district. A remarkable feature is shown in the proximal ends of three of the rhabdosomes, where the sicula terminates, not in a nema, but in a little tuft of root-like fibres.

Our knowledge of the geology of the district fringing the Grampians in Perthshire and Angus has been limited in the main to the published 1 inch maps of H.M. Geological Survey of Scotland (Sheets 48 and 56 in particular). A few papers in the Quarterly Journal of the Geological Society about the middle of the last century deal with certain exposures of special interest. The writer of the present contribution has conducted recently a detailed investigation of the area between Dunkeld and Fern, and an account of the solid geology has been published. The glacial geology presents no less interesting material or problems and, while the major portion of the results is being held over until further field-work is undertaken, one aspect, and over a limited area, will be considered here.

In a study of the surface features of our satellite one is immediately struck by the remarkable sharpness and freshness which most of those features exhibit. Further, one is impressed by the fact that evidences of compressive action are in the minority, whereas the moon's crust shows clearly innumerable clefts, rifts, and fractures pointing to an extensional tendency of its outer envelope. This is hardly in accordance with our ideas of the appearance of a sphere which has lost all its heat; everywhere it should show signs of intense contraction, and arcuate mountain ranges should be more frequent than upon the face of the earth.

This paper gives the results of a series of analyses of typical schists occurring in the Eastern Desert of Egypt. So far as we are aware, no study of this group of metamorphic rocks has as yet been undertaken as regards Egypt itself. Yet this method of attack is essential if any knowledge is to be obtained, not only of their structure and composition, but also of their origin. It must not be forgotten that schists occupy vast areas in south-eastern Egypt, and are also present in Sinai; also among them are included varieties derived from igneous and volcanic rocks as well as from ancient sediments.

The Province of Huelva, famed for its mines from the times of the Ancients, lies in the south-western portion of Spain, in the upland between the basins of the Guadalquivir and Guadiana. To the north are the serrated ridges of the Sierra Morena and to the south the fertile plains of Huelva and Sevilla. This upland, now in a mature stage of erosion, forms the old coastal plain. It is composed of Palaeozoic rocks, chiefly Carboniferous, which lie unconformably on the pre-Cambrian gneisses and schists of the Sierra Morena. Miocene limestone and Pleistocene Drift in places obscure the Palaeozoic rocks. The Carboniferous rocks are principally slates and grits, the former being by far the more abundant. In what is usually regarded as Hercynian times and following great tectonic movements, the Carboniferous rocks were invaded by granites, porphyries, diorites, porphyrites, and diabase. The mineralization was associated with these intrusives and principally with the porphyries. Finally the area was reduced to a peneplain by erosion.

It is now eight years since the present writer drew attention in these pages to his discovery of a diamond-bearing pipe of igneous origin in Brazil (3). The matter, though hotly contested and denied at the time, seems now to have been generally accepted. So much so in fact that Dr. Alex. du Toit, in his presidential address to the Geological Society of South Africa (10) compares the diamond-bearing pipes of Brazil and South Africa as an indication of the former close connection of these lands.

The precise age of the Millstone Grit of South Wales has been in doubt for some years. Although it has been shown to be of Upper Carboniferous age, it has been uncertain whether the whole of the earliest part of the Upper Carboniferous is represented by deposits in southern Britain. Some part of the Millstone Grit of Pembrokeshire has been regarded, on the basis of its flora, as of Middle Coal Measure or Yorkian age (Goode, 1913, p. 272). Similar conclusions have been reached by Dr. R. Crookall concerning part of the Millstone Grit of Somerset (1925, p. 403). As yet, the flora characteristic of the Lanarkian of northern Britain has not been proved to be present in South Wales and elsewhere in south Britain. On the other hand, it has been argued that the absence of a Lanarkian flora does not necessarily imply an important break in the sequence, since recent work on the lamellibranch fauna of various British coalfields points to the conclusion that the lowest part of the Lower Coal Series of South Wales is of approximately the same age as the Lower Coal Measures of northern England (Davies and Trueman, 1927, p. 253).